Aging is associated with decreased cellular function and a decreased ability of the organism to adapt to physical stress. Since membranes play a primary role in the regulation of important physiological and biochemical functions, we will test whether part of the decreased function and adaptibility results from aging of the cellular membrane. We will also investigate the interrelation between aging of the membrane and the increased severity of certain major diseases in the aged. We have chosen the kidney as the organ to study these problems, since 1) the general function of this organ declines with age, 2) we have previously demonstrated changes in membrane composition and function with age, and 3) specific renal diseases are more serious in elderly than in younger patients. The specific effects of aging will be studied on membrane metabolism, biogenesis, and binding characteristics during the course of two major conditions: acute renal failure and chronic renal failure. Techniques of study on aged rats will include metabolic assays, measurements of membrane-bindings, and the characterization of membrane-bound enzymes. The long term goal is to understand the universal process of aging, especially the mechanisms that lead to cellular aging and reduced ability to withstand the stress of disease.